In vivo identification of colonic dysplasia using fluorescence endoscopic imaging

Ex vivo photometric and polarimetric multilayer characterization of human healthy colon by multispectral Mueller imaging

Healthy human colon samples were analyzed ex vivo with a multispectral imaging Mueller polarimeter operating from 500 to 700 nm in a backscattering configuration with diffuse light illumination impinging on the innermost tissue layer, the mucosa. The intensity and polarimetric responses were taken on whole tissues first and after progressive exfoliation of the outer layers afterwards. Moreover, these measurements were carried out with two different substrates (one bright and the other dark) successively placed beneath each sample, allowing a reasonably accurate evaluation of the contributions to the overall backscattered light by the various layers. For the shorter investigated wavelengths (500 to 550 nm) the major contribution comes from mucosa and submucosa, while for the longer wavelengths (650 to 700 nm) muscular tissue and fat also contribute significantly. The depolarization has also been studied and is found to be stronger in the red part of the spectrum, mainly due to the highly depolarizing power of the muscular and fat layers.

Endoscopic imaging of Cerenkov luminescence

We demonstrate feasibility of endoscopic imaging of Cerenkov light originated when charged nuclear particles, emitted from radionuclides, travel through a biological tissue of living subjects at superluminal velocity. The endoscopy imaging system consists of conventional optical fiber bundle/ clinical endoscopes, an optical imaging lens system, and a sensitive low-noise charge coupled device (CCD) camera. Our systematic studies using phantom samples show that Cerenkov light from as low as 1 µCi of radioactivity emitted from (18)F-Fluorodeoxyglucose (FDG) can be coupled and transmitted through conventional optical fibers and endoscopes. In vivo imaging experiments with tumor bearing mice, intravenously administered with (18)F-FDG, further demonstrated that Cerenkov luminescence endoscopy is a promising new tool in the field of endoscopic molecular imaging.

Targeted detection of murine colonic dysplasia in vivo with flexible multispectral scanning fiber endoscopy

Gastrointestinal cancers are heterogeneous and can overexpress several protein targets that can be imaged simultaneously on endoscopy using multiple molecular probes. We aim to demonstrate a multispectral scanning fiber endoscope for wide-field fluorescence detection of colonic dysplasia. Excitation at 440, 532, and 635 nm is delivered into a single spiral scanning fiber, and fluorescence is collected by a ring of light-collecting optical fibers placed around the instrument periphery. Specific-binding peptides are selected with phage display technology using the CPC;Apc mouse model of spontaneous colonic dysplasia. Validation of peptide specificity is performed on flow cytometry and in vivo endoscopy. The peptides KCCFPAQ, AKPGYLS, and LTTHYKL are selected and labeled with 7-diethylaminocoumarin-3-carboxylic acid (DEAC), 5-carboxytetramethylrhodamine (TAMRA), and CF633, respectively. Separate droplets of KCCFPAQ-DEAC, AKPGYLS-TAMRA, and LTTHYKL-CF633 are distinguished at concentrations of 100 and 1 μM. Separate application of the fluorescent-labeled peptides demonstrate specific binding to colonic adenomas. The average target/background ratios are 1.71 ± 0.19 and 1.67 ± 0.12 for KCCFPAQ-DEAC and AKPGYLS-TAMRA, respectively. Administration of these two peptides together results in distinct binding patterns in the blue and green channels. Specific binding of two or more peptides can be distinguished in vivo using a novel multispectral endoscope to localize colonic dysplasia on real-time wide-field imaging.

Tryptophan autofluorescence imaging of neoplasms of the human colon

Detection of flat neoplasia is a major challenge in colorectal cancer screening, as missed lesions can lead to the development of an unexpected 'incident' cancer prior to the subsequent endoscopy. The use of a tryptophan-related autofluorescence has been reported to be increased in murine intestinal dysplasia. The emission spectra of cells isolated from human adenocarcinoma and normal mucosa of the colon were studied and showed markedly greater emission intensity from cancerous cells compared to cells obtained from the surrounding normal mucosa. A proto-type multispectral imaging system optimized for ultraviolet macroscopic imaging of tissue was used to obtain autofluorescence images of surgical specimens of colonic neoplasms and normal mucosa after resection. Fluorescence images did not display the expected greater emission from the tumor as compared to the normal mucosa, most probably due to increased optical absorption and scattering in the tumors. Increased fluorescence intensity in neoplasms was observed however, once fluorescence images were corrected using reflectance images. Tryptophan fluorescence alone may be useful in differentiating normal and cancerous cells, while in tissues its autofluorescence image divided by green reflectance may be useful in displaying neoplasms.

In vivo diagnosis of colonic precancer and cancer using near-infrared autofluorescence spectroscopy and biochemical modeling

The aim of this study is to evaluate the biochemical foundation and clinical capability of an image-guided near-infrared (NIR) autofluorescence (AF) spectroscopy technique for in vivo diagnosis of colonic malignancies during clinical colonoscopy. A novel endoscopic fiber-optic AF system was utilized for in vivo NIR AF measurements at 785 nm excitation. A total of 263 in vivo NIR AF spectra of colonic tissues were measured from 100 patients, in which 164 spectra were from benign tissue (116 normal and 48 hyperplastic polyps), 34 spectra were from precancer (adenomatous polyps), and 65 spectra were from cancer. The non-negativity constrained least squares minimization biochemical modeling was explored to estimate the biochemical compositions of colonic tissue using nine basis reference spectra from the representative biochemicals (i.e., collagen I, elastin, β-nicotinamide adenine dinucleotide, flavin adenine dinucleotide, L-tryptophan, hematoporphyrin, 4-pyridoxic acid, pyridoxal 5'-phosphate, and water) associated with structural or cellular metabolic progression in colonic precancer and cancer. High-quality in vivo NIR AF spectra in the spectral range of 810 to 1000 nm were acquired from colonic benign, precancerous, and cancerous mucosa under white-light reflectance endoscopic imaging guidance. Partial least squares discriminant analysis, together with the leave-one tissue site-out, cross validation on in vivo NIR AF spectra yields diagnostic sensitivities of 85.4%, 76.5%, and 84.6%, and specificities of 89.9%, 93.4%, and 91.4%, respectively, for classification of benign, precancer, and cancer in the colon. This work demonstrates that image-guided NIR AF spectroscopy in conjunction with biochemical modeling has promising potential for improving in vivo detection and diagnosis of colonic precancer and cancer during clinical colonoscopic screening.

Wide-field fluorescence lifetime imaging of cancer

Optical imaging of tissue autofluorescence has the potential to provide rapid label-free screening and detection of surface tumors for clinical applications, including when combined with endoscopy. Quantitative imaging of intensity-based contrast is notoriously difficult and spectrally resolved imaging does not always provide sufficient contrast. We demonstrate that fluorescence lifetime imaging (FLIM) applied to intrinsic tissue autofluorescence can directly contrast a range of surface tissue tumors, including in gastrointestinal tissues, using compact, clinically deployable instrumentation achieving wide-field fluorescence lifetime images of unprecedented clarity. Statistically significant contrast is observed between cancerous and healthy colon tissue for FLIM with excitation at 355 nm. To illustrate the clinical potential, wide-field fluorescence lifetime images of unstained ex vivo tissue have been acquired at near video rate, which is an important step towards real-time FLIM for diagnostic and interoperative imaging, including for screening and image-guided biopsy applications.

Strategies for high-resolution imaging of epithelial ovarian cancer by laparoscopic nonlinear microscopy

Ovarian cancer remains the most frequently lethal of the gynecologic cancers owing to the late detection of this disease. Here, by using human specimens and three mouse models of ovarian cancer, we tested the feasibility of nonlinear imaging approaches, the multiphoton microscopy (MPM) and second harmonic generation (SHG) to serve as complementary tools for ovarian cancer diagnosis. We demonstrate that MPM/SHG of intrinsic tissue emissions allows visualization of unfixed, unsectioned, and unstained tissues at a resolution comparable to that of routinely processed histologic sections. In addition to permitting discrimination between normal and neoplastic tissues according to pathological criteria, the method facilitates morphometric assessment of specimens and detection of very early cellular changes in the ovarian surface epithelium. A red shift in cellular intrinsic fluorescence and collagen structural alterations have been identified as additional cancer-associated changes that are indiscernible by conventional pathologic techniques. Importantly, the feasibility of in vivo laparoscopic MPM/SHG is demonstrated by using a "stick" objective lens. Intravital detection of neoplastic lesions has been further facilitated by low-magnification identification of an indicator for cathepsin activity followed by MPM laparoscopic imaging. Taken together, these results demonstrate that MPM may be translatable to clinical settings as an endoscopic approach suitable for high-resolution optical biopsies as well as a pathology tool for rapid initial assessment of ovarian cancer samples.

An endoscopic training model to improve accuracy of colonic polyp size measurement

PURPOSE

Most studies of colonic polyps rely on visual estimation when regarding polyp size; however, the reliability of a visual estimate is questionable. Our study aims to develop a training model to improve the accuracy of size estimation of colonic polyps in vivo.

METHODS

Colon polyps were recorded on 160 video clips during colonoscopy. The size of each polyp was estimated by visual inspection and subsequently measured with a flexible linear measuring probe. The study included a pretest, an intervention, and a posttest. The pretest included 160 video clips, which comprised the visual-estimation portion of the study. The intervention was an educational model consisting of 30 video clips which included a visual-estimation section and a linear-measuring-probe section, designed to help the endoscopists to compare their visual estimate of size with the measured size of the polyps. The posttest included the 160 video clips used in the pretest, presented in random order. Intraobserver agreement and diagnostic accuracy were compared before and after the training session.

RESULTS

Eight beginners and four experienced colonoscopists were enrolled. The overall kappa (kappa) values of intraobserver agreement for pretest and posttest were 0.74 and 0.85 for beginner group as well as 0.83 and 0.88 for experienced group, respectively. The overall diagnostic accuracy improved from 0.52 to 0.78 for beginner group and 0.71 to 0.87 for experienced group (P < 0.05) after education with the training model.

CONCLUSIONS

This training model could help endoscopists improve the accuracy of measurement of polyps on colonoscopy in a short period. The durability of learning effect needs further investigation.

Co-registered optical coherence tomography and fluorescence molecular imaging for simultaneous morphological and molecular imaging

Optical coherence tomography (OCT) provides high-resolution, cross-sectional imaging of tissue microstructure in situ and in real time, while fluorescence molecular imaging (FMI) enables the visualization of basic molecular processes. There is a great deal of interest in combining these two modalities so that the tissue's structural and molecular information can be obtained simultaneously. This could greatly benefit biomedical applications such as detecting early diseases and monitoring therapeutic interventions. In this research, an optical system that combines OCT and FMI was developed. The system demonstrated that it could co-register en face OCT and FMI images with a 2.4 x 2.4 mm(2) field-of-view. The transverse resolutions of OCT and FMI of the system are both approximately 10 microm. Capillary tubes filled with fluorescent dye Cy 5.5 in different concentrations under a scattering medium are used as the phantom. En face OCT images of the phantoms were obtained and successfully co-registered with FMI images that were acquired simultaneously. A linear relationship between FMI intensity and dye concentration was observed. The relationship between FMI intensity and target fluorescence tube depth measured by OCT images was also observed and compared with theoretical modeling. This relationship could help in correcting reconstructed dye concentration. Imaging of colon polyps of the APC(min) mouse model is presented as an example of biological applications of this co-registered OCT/FMI system.

Narrow Band Imaging and Autofluorescence Imaging for the Detection and Optical Diagnosis of Colorectal Polyps

Colorectal cancer is the most common cancer in Singapore and polyps which are detected during screening colonoscopy are routinely removed. Conventional white light colonoscopy has a substantial miss-rate for polyps and limited accuracy in differentiating neoplastic from non-neoplastic polyps. Dye-based chromoendoscopy and more recent equipment-based image enhanced endoscopic techniques such as narrow-band imaging (NBI) and autofluorescence imaging (AFI) are promising tools to improve polyp detection and optical diagnosis. Current evidence suggests that NBI may not be superior compared to high definition white-light for polyp detection, but it achieves excellent accuracy in polyp characterisation, approaching that of histopathology. AFI is a wide area scanning modality which functions as a red-flag technique to improve polyp detection, although the evidence is still evolving. The ability to accurately characterise polyps with NBI and AFI will guide the management of polyps and in some cases, avoid unnecessary polypectomy and routine histopathology. This has potential to reduce associated costs and risks of polypectomy, and improves on overall efficiency of screening colonoscopy. The review will discuss the technology, current evidence and the issues relevant to the role of NBI and AFI for the detection and optical diagnosis of polyps in colorectal cancer screening.

Trimodal imaging endoscopy may improve diagnostic accuracy of early gastric neoplasia: a feasibility study

BACKGROUND

A considerable number of superficial gastric neoplasias are overlooked with conventional white light imaging (WLI) endoscopy.

OBJECTIVE

The aim was to investigate the diagnostic potential of trimodal imaging endoscopy (TME), which combines WLI, autofluorescence imaging (AFI), and narrow-band imaging (NBI), for superficial gastric neoplasia.

DESIGN

Feasibility study.

SETTING

Single academic center.

PATIENTS

Sixty-two patients with or without gastric neoplasia.

INTERVENTION

Each patient serially assessed with WLI, AFI, and magnifying endoscopy with NBI (ME-NBI) by an endoscopist blinded for clinical information. ME-NBI over WLI and AFI was designated as TME. Histopathology of biopsy and ESD specimens was evaluated and used as the gold standard.

MAIN OUTCOME MEASUREMENTS

Sensitivity and specificity of endoscopic diagnosis of pathology-proven neoplasia by per-patient and per-lesion analyses.

RESULTS

The study included 47 pathology-proven neoplasias and 44 pathology-proven nonneoplasias that were detected as neoplasias with any of the modalities. By a per-lesion analysis, the sensitivity of TME (89.4%) was higher than that of WLI (76.6%) and AFI (68.1%). The specificity of TME (98.0%) was higher than that of WLI (84.3%) and AFI (23.5%). By a per-patient analysis, the sensitivity of TME (90.9%) was higher than that of WLI (75%) and AFI (68.2%). The specificity of TME (100%) was higher than that of WLI (72.2%) and AFI (44.4%).

LIMITATIONS

Case-enriched population at a single center.

CONCLUSIONS

Higher diagnostic accuracy of TME over conventional WLI indicates the feasibility of TME for the efficacious diagnosis of early gastric neoplasia.

Combining autofluorescence imaging and narrow-band imaging for the differentiation of adenomas from non-neoplastic colonic polyps among experienced and non-experienced endoscopists

OBJECTIVES

Endoscopic tri-modal imaging incorporates high-resolution white-light endoscopy (HR-WLE), narrow-band imaging (NBI), and autofluorescence imaging (AFI). Combining these advanced techniques may improve endoscopic differentiation between adenomas and non-neoplastic polyps. In this study, we aimed to assess the interobserver variability and accuracy of HR-WLE, NBI, and AFI for polyp differentiation and to evaluate the combined use of AFI and NBI.

METHODS

First, still images of 50 polyps (22 adenomas; median 3 mm) were randomly displayed to three experienced and four non-experienced endoscopists. All HR-WLE and NBI images were scored for Kudo classification and AFI images for color. Second, the combined AFI and NBI images were assessed using a newly developed algorithm by six additional non-experienced endoscopists.

RESULTS

The outcomes measured were interobserver agreement and diagnostic accuracy using histopathology as reference standard. Experienced endoscopists had better interobserver agreement for NBI (kappa=0.77) than for AFI (kappa=0.33), whereas non-experienced endoscopists had better agreement for AFI (kappa=0.58) than for NBI (kappa=0.33). The accuracies of HR-WLE, NBI, and AFI among experienced endoscopists were 65, 70, and 74, respectively. Figures among non-experienced endoscopists were 57, 63, and 77. The algorithm was associated with a significantly higher accuracy of 85% among all observers (P<0.023). These figures were confirmed in the second evaluation study.

CONCLUSIONS

Non-experienced endoscopists have better interobserver agreement and accuracy for AFI than for HR-WLE or NBI, indicating that AFI is easier to use for polyp differentiation in non-experienced setting. The newly developed algorithm, combining information of AFI and NBI together, had the highest accuracy and obtained equal results between experienced and non-experienced endoscopists.

Clinical evaluation of endoscopic trimodal imaging for the detection and differentiation of colonic polyps

BACKGROUND & AIMS

Endoscopic trimodal imaging (ETMI) incorporates high-resolution endoscopy (HRE) and autofluorescence imaging (AFI) for adenoma detection, and narrow-band imaging (NBI) for differentiation of adenomas from nonneoplastic polyps. The aim of this study was to compare AFI with HRE for adenoma detection and to assess the diagnostic accuracy of NBI for differentiation of polyps. This was a randomized trial of tandem colonoscopies. The study was performed at the Academic Medical Center in Amsterdam.

METHODS

One hundred patients underwent colonoscopy with ETMI. Each colonic segment was examined twice for polyps, once with HRE and once with AFI, in random order per patient. All detected polyps were assessed with NBI for pit pattern and with AFI for color, and subsequently removed. Histopathology served as the gold standard for diagnosis. The main outcome measures of this study were adenoma miss-rates of AFI and HRE, and diagnostic accuracy of NBI and AFI for differentiating adenomas from nonneoplastic polyps.

RESULTS

Among 50 patients examined with AFI first, 32 adenomas were detected initially. Subsequent inspection with HRE identified 8 additional adenomas. Among 50 patients examined with HRE first, 35 adenomas were detected initially. Successive AFI yielded 14 additional adenomas. The adenoma miss-rates of AFI and HRE therefore were 20% and 29%, respectively (P = .351). The sensitivity, specificity, and overall accuracy of NBI for differentiation were 90%, 70%, and 79%, respectively; corresponding figures for AFI were 99%, 35%, and 63%, respectively.

CONCLUSIONS

The overall adenoma miss-rate was 25%; AFI did not significantly reduce the adenoma miss-rate compared with HRE. Both NBI and AFI had a disappointing diagnostic accuracy for polyp differentiation, although AFI had a high sensitivity.

Current application of confocal endomicroscopy in gastrointestinal disorders

Confocal endomicroscopy (CEM) is a recent advancement in imaging technology that incorporates a confocal laser microscope into the tip of a flexible endoscope. The 1000-fold magnification and high resolution allows for real time in vivo histology or "virtual biopsies" of the gastrointestinal tract mucosa. CEM has the capability to instantaneously diagnose intra-epithelial neoplasia during endoscopy, alone or in combination with a "red-flag" technique, such as chromoendoscopy. Therefore, there is clinical utility in the surveillance or diagnosis of Barrett's esophagus, gastric intestinal metaplasia and cancer, longstanding ulcerative colitis, and colonic neoplasia. Furthermore, CEM also appears to be useful in the evaluation of coeliac disease, microscopic colitis, and in diagnosing Helicobacter pylori chronic gastritis. This review examines the current available data on the utility of this new technology in clinical gastroenterology and its potential impact in the future.

Scanning single fiber endoscopy: a new platform technology for integrated laser imaging, diagnosis, and future therapies

Remote optical imaging of human tissue in vivo has been the foundation for the growth of minimally invasive medicine. This article describes a new type of endoscopic imaging that has been developed and applied to the human esophagus, pig bile duct, and mouse colon. The technology is based on a single optical fiber that is scanned at the distal tip of an ultrathin and flexible shaft that projects red, green, and blue laser light onto tissue in a spiral pattern. The resulting images are high-quality color video that is expected to produce future endoscopes that are thinner, longer, more flexible, and able to directly integrate the many recent advances of laser diagnostics and therapies.

Fluoroquinolone antibiotics having the potential to interfere with fluorescence-based diagnosis

Fluorescence, both intrinsic and exogenously induced, is being used for diagnosis of abnormal tissue. Excitation wavelengths used by these methods range from 320 to 450 nm. The presence of absorbing or fluorescing drugs is rarely taken into account by practitioners of fluorescence diagnosis and has the potential to yield false-positive or false-negative results. Our aim is to quantify this potential by (1) comparing the quantum yield of fluoroquinolone antibiotics to those of known tissue fluorophores and (2) taking into account drug concentrations in the tissue during treatment. Quantum yields are determined relative to a working standard of Rhodamine 6G in ethanol. The working standard was calibrated against a fluorescein standard. We concentrated our initial efforts on (1) the fluoroquinolone antibiotics, ciprofloxacin, norfloxacin and ofloxacin and (2) the intrinsic tissue fluorophores, NADH, FAD and protoporphyrin IX. When ciprofloxacin, norfloxacin and ofloxacin were excited at wavelengths 310-390 nm, emission occurred from 350 to 650 nm with quantum yields ranging from 0.03 to 0.3. Quantum yields for intrinsic fluorophores excited at their peak absorption wavelengths were 0.02 (NADH, 340 nm), 0.035 (FAD, 450 nm) and 0.087 (protoporphyrin IX, 408 nm). A review of the literature shows that these fluoroquinolones have a large volume of distribution and can be found in high concentrations in almost every organ during a treatment regimen. The product of the drug tissue concentration and quantum yield, which we term the fluorescence effective concentration, is such that it is likely these fluoroquinolones will interfere during fluorescence diagnosis techniques.

Review article: New developments in colonic imaging

BACKGROUND

Colonoscopic detection and removal of neoplasia from the colorectum prevent the development of colorectal cancer. Sporadic adenomas and neoplasia associated with ulcerative colitis are frequently missed during colonoscopy, as a result of which, interval cancers might develop.

AIM

To review new developments in colonoscopic imaging concerning the detection of neoplasia.

METHODS

Medical databases were searched for relevant publications, dealing with advanced endoscopic imaging techniques during colonoscopy.

RESULTS

Pancolonic chromoendoscopy has shown to increase the detection of sporadic adenomas and ulcerative colitis associated neoplasia, at the expense of longer examination times. As chromoendoscopy is labour intensive and time-consuming, its widespread use has been hampered. Narrow band imaging is a novel endoscopic imaging technique, which enhances mucosal and vascular details. Recent studies indicate that narrow band imaging has a high yield for neoplasia; however, no improvement compared to standard colonoscopy has been demonstrated. Autofluorescence imaging is another new technique for which blue endoscopic light is used to induce mucosal autofluorescence. So far, preliminary results have shown promising results of autofluorescence imaging for neoplasia detection.

CONCLUSION

Whether chromoendoscopy or novel advanced imaging techniques will change current colonoscopic practice depends on results of future studies comparing these different colonoscopic techniques.

Techniques for targeting screening in ulcerative colitis

Patients with longstanding chronic ulcerative colitis are "at risk" of developing colorectal cancer. Approximately 1 in 6 patients will die as a result of colorectal malignancy, which can often be difficult to detect using conventional "white light" colonoscopy. New endoscopic techniques and technologies including the use of dye sprays, "chromoendoscopy", high magnification chromoscopic colonoscopy and recently chromoscopic assisted confocal laser scanning in vivo endomicroscopy have now been introduced to improve the diagnostic yield of intraepithelial neoplasia at screening colonoscopy. This review details the true "risk" of colorectal cancer complicating ulcerative colitis, discusses the objective evidence to support current endoscopic screening guidelines, and describes the imminent technological paradigm shift about to occur in the endoscopic management and detection of intraepithelial neoplasia.

Novel colorectal endoscopic in vivo imaging and resection practice: a short practice guide for interventional endoscopists

Colorectal cancer remains a leading cause of cancer death in the UK. With the advent of screening programmes and developing techniques designed to treat and stage colorectal neoplasia, there is increasing pressure on the colonoscopist to keep up to date with the latest practices in this area. This review looks at the basic principles behind endoscopic mucosal resection and forward to the potential endoscopic tools, including high-magnification chromoscopic colonoscopy, high-frequency miniprobe ultrasound and confocal laser scanning endomicroscopic colonoscopy, that may soon become part of routine colorectal cancer management.

Autofluorescence properties of rat cerebellum cortex during postnatal development

BACKGROUND AND OBJECTIVES

The multilayered structure of rat neocerebellum cortex (VI-VIII lobules of the vermis) during postnatal development undergoes rearrangements, which in turn are affected by treatment with the anti-tumoral drug cisplatin. The dependence of autofluorescence emission properties on the tissue structural and molecular features has been investigated.

STUDY DESIGN/MATERIALS AND METHODS

Autofluorescence analysis was performed at defined time points of cerebellar histogenesis--11, 17, and 30 postnatal days- under normal conditions or after 5 microg/g body weight cisplatin treatment at 10 postnatal day. Autofluorescence signal was analyzed in vivo at the surface of intact lobules of cerebellum vermis by means of fiber optic spectrofluorometry, or on tissue sections by means of microspectrofluorometry and fluorescence imaging.

RESULTS

In vivo spectroscopy showed changes of autofluorescence signal both during normal histogenesis and after cisplatin treatment. External granular layer (EGL) and molecular layer (ML), that is, the more external layers were found to be interested by structural alterations, and showed the greatest changes in signal amplitude, accounting for the in vivo results. Fitting analysis indicated that changes in spectral shape reflected an increase in oxidative damages induced by cisplatin treatment.

CONCLUSIONS

The results confirm the relationship of the autofluorescence emission properties with histological and biochemical features of biological tissue.

Integrated dynamic fluidic lens system for in vivo biological imaging

We have developed an integrated dynamic lens system for in vivo optical imaging. Bioinspired dynamic microfluidic lenses allow for real-time dynamic manipulation of the lens focal length via microfluidic injection into a PDMS membrane-capped chamber. A piezoelectrically actuated micropump is integrated with with the lens to provide highspeed, accurate lens tunability. The 5mm dynamic lens has demonstrated focal length tunability from 8.5mm to 23mm, numerical aperture values from 0.39 to 0.77, and resolution of 40 linepairs/mm. The micropump operates at 5 kHz and achieved a flow rate of approximately 2.4 mL/min. This system can be applied to optical probe techniques to improve diagnosis with real-time depth resolution and variable numerical aperture.

Optical adjuncts for enhanced colonoscopic diagnosis

Background

Optical techniques using previously unexploited properties of light interaction with tissue may be valuable in the detection, diagnosis and staging of colorectal neoplasia.

Methods

A Medline search (1990 to present) was conducted on optical diagnostics in the detection of colorectal neoplasia. The reference list of each identified article was reviewed for further relevant papers.

Results and conclusion

Chromoendoscopy is the only optical adjunct to colonoscopy that has been tested in large randomized clinical trials. It improves the detection of small and flat colorectal adenomas, and of neoplasia in chronic ulcerative colitis and hereditary non-polyposis colorectal cancer. All other techniques are the subject of ongoing research and the practicality of population screening with any of the methods has yet to be established. Optical techniques may, however, permit immediate clinical diagnosis, removing the need for histological analysis. They may also improve the diagnosis of early colonic neoplasia.

Advanced imaging and technology in gastrointestinal neoplasia: summary of the AGA-NCI Symposium October 4-5, 2004

Imaging and other advanced technologies for detection of gastrointestinal cancers are undergoing a major revolution on several fronts. This is facilitated by convergence of key technologies including advanced endoscopic-detection systems, more specific contrast agents, rapid and high-resolution cross-sectional imaging, and miniaturization of construction systems for making all imaging equipment smaller and less invasive. This convergence is occurring along traditional translational research pathways (clinical medicine-molecular biology) as well as nontraditional lines (clinical medicine-optical physics/engineering and molecular biology-optical physics/engineering). These new efforts are producing a wide array of technologies aimed at improving detection, classification, and monitoring of gastrointestinal neoplasia, especially for colorectal and esophageal cancer because of easier accessibility. A critical goal is to detect lesions at their premalignant stages, thereby permitting meaningful intervention. Inspired by these advances, the American Gastroenterological Association and the National Cancer Institute sponsored a symposium held in Bethesda, MD, from October 4-5, 2004, bringing together leading investigators with diverse backgrounds in imaging technology. The aims of this symposium were to summarize the state of the art and priorities for research in the coming decade in the field of imaging and advanced technology for gastrointestinal neoplasia. In this overview, we summarize the salient results of that symposium. The initial sections discuss the major technologies in each area of endoluminal imaging and molecular imaging followed by applications to specific diseases such as Barrett's esophagus and colon neoplasia. Each section focuses on the current state of the art then lists major priorities for research in the field.

Elastic scattering spectroscopy for the diagnosis of colonic lesions: initial results of a novel optical biopsy technique

BACKGROUND

Biopsy and polypectomy frequently are performed for lesions that carry a low risk of malignant transformation in the colon. Elastic scattering spectroscopy (ESS) is a novel optical biopsy technique that can distinguish, almost instantaneously, between normal and abnormal tissue in vivo, without the need to remove tissue. We assessed the diagnostic potential of ESS in the colon to differentiate normal colonic mucosa, chronic colitis, hyperplastic polyps, adenomatous polyps (with dysplasia), and adenocarcinoma.

METHODS

ESS spectra were obtained from 138 sites in 45 patients at colonoscopy. They were then compared with conventional biopsy specimens taken from the same site, including normal colonic mucosa, hyperplastic polyps, adenomatous polyps, chronic colitis, and colon cancer. Spectral analysis was carried out with a validated computerized model that used principal component analysis followed by linear discriminant analysis. Cross validation was carried out by using 60% of the data as a "training set" and the remaining 40% of the data as a "test set."

RESULTS

A total of 483 spectra were analyzed (290 normal, 19 hyperplastic, 69 adenomatous polyps, 74 chronic colitis, and 31 colorectal cancer). The sensitivity and the specificity of differentiating adenomas from hyperplastic polyps was 84% and 84%, respectively; for cancer from adenomatous polyps, 80% and 75%, respectively; for colitis from normal tissue, 77% and 82%, respectively; and for dysplastic mucosa (from polyps) from colitis, 85% and 88%, respectively.

CONCLUSIONS

ESS holds promise for differentiating colonic lesions with good accuracy and, therefore, is a potentially useful tool to make an instantaneous diagnosis during colonoscopy. It could prove a valuable aid for targeting biopsies in dysplasia surveillance in inflammatory bowel disease and for deciding which small polyps should be removed.

OPTICAL SPECTROSCOPY CHARACTERISTICS CAN DIFFERENTIATE BENIGN AND MALIGNANT RENAL TISSUES: A POTENTIALLY USEFUL MODALITY

PURPOSE

Promising results of optical signals have been reported in the literature for the diagnosis of Barrett's esophagus, oral cavity lesions, brain tumor margins, cervical intraepithelial neoplasia, skin cancer and bladder cancer. The potential usefulness of these techniques in renal tissues and neoplasms has not been described to date. This initial study examined the feasibility of using fluorescence and diffuse reflectance spectroscopy to differentiate between malignant and benign renal tissues.

MATERIALS AND METHODS

An ex vivo study was conducted to identify optical characteristics of various renal tissue types. Pathologically confirmed benign and malignant renal samples were obtained from nephrectomy specimens from patients undergoing radical nephrectomy. Fluorescence and diffuse reflectance spectra were measured from benign and malignant renal tissues.

RESULTS

All renal tissues, malignant or benign, contain 2 primary emission peaks-a strong one at approximately 285 nm excitation, approximately 340 nm emission (Peak A), and a weak one at approximately 340 nm excitation, approximately 460 nm emission (Peak B). Peak A of normal renal tissue typically locates at the shorter excitation wavelength region than that of malignant tissue. The intensity of Peak B from benign tissues tends to be greater than that from malignant renal tissues. Diffuse reflectance intensities from malignant renal tissues between 600 and 800 nm are markedly greater than those from normal renal tissue. Empirical discrimination algorithms developed based on selected fluorescence and diffuse reflectance spectral characteristics yields accurate differentiation between benign and malignant renal tissues.

CONCLUSIONS

Highly accurate differentiation between normal human renal tissues and renal cell cancers is feasible using combined fluorescence and diffuse reflectance spectroscopy in an ex vivo setting. If successful in future clinical studies, optical spectroscopy could aid in margin detection and tissue discrimination while performing nephron sparing surgery.

New imaging techniques at colonoscopy: tissue spectroscopy and narrow band imaging

Although colonoscopy has undergone impressive development in recent decades, there remains a need for better endoscopic visualization in specific circumstances (eg, dysplasia screening in ulcerative colitis and detection of flat colorectal lesions). Many techniques are under investigation; this article discusses different forms of spectroscopy and narrow band imaging. Ideal colonoscopy should have high diagnostic accuracy and the ability to screen large mucosal areas. The most successful clinical method probably will be a combination of techniques, providing wide-area surveillance (such as fluorescence endoscopy or immunoscopy) and point detection methods, such as narrow band imaging or confocal microendoscopy, that can be used to identify the lesion further.

Advances in colonic imaging: new endoscopic imaging methods

There is a need for better endoscopic visualization in specific circumstances like detection of flat colorectal lesions and dysplasia-screening in ulcerative colitis. Chromoendoscopy is a technique with proven success, but many more, novel endoscopic techniques are currently under investigation. In this article different point measurement and still imaging methods are discussed: Raman spectroscopy, elastic (light) scattering spectroscopy, fluorescence spectroscopy, optical coherence tomography and confocal laser microscopy. Furthermore, real-time endoscopic imaging methods are discussed. These include narrow band imaging, fluorescence imaging and endocytoscopy. The results of fluoroscence imaging might be improved by application of photosensitizers or coupling of fluorescent dyes to tumour-related antigens (immunoscopy). Most of these techniques still have to be developed further and are not yet available for routine use. In our opinion, a combination of a red-flag technique and a microscopic technique carries an enormous potential.

New frontiers in endoscopic imaging

Gastrointestinal (GI) tract malignancies have a tremendous impact on society. Colorectal cancer is the second leading cause of cancer death in the United States and accounts for 10% of all cancer deaths. Significant research efforts are being directed toward using the interaction of light and tissue to detect pre-cancerous lesions of the GI tract. This article reviews the current status of various experimental optical technologies to detect pre-cancerous changes in the GI tract and focuses on the clinical applications of these technologies for the practicing gastroenterologist.

High-sensitivity and specificity of laser-induced autofluorescence spectra for detection of colorectal cancer with an artificial neural network

An artificial neural network (ANN) has been used in various clinical research for the prediction and classification of data in cancer disease. Previous research in this direction focused on the correlation between various input parameters such as age, antigen, and size of tumor growth. Recently, laser-induced autofluorescence (LIAF) techniques have been shown to be a useful noninvasive early diagnostic tool for various cancer diseases. We report on a successful application of ANN to in vitro LIAF spectra. We show that classification of tumor samples with ANN can be done with high sensitivity, specificity, and accuracy. Thus a combination of LIAF techniques and ANN can provide a robust method for clinical diagnosis.

The status of in vivo autofluorescence spectroscopy and imaging for oral oncology

Autofluorescence spectroscopy and imaging have been studied for the early detection and classification of (pre)malignancies of the oral mucosa. In the present review we will give an overview of the literature on autofluorescence imaging and spectroscopy for various clinical questions. From the studies performed so far we hope to conclude whether autofluorescence spectroscopy and imaging are helpful in the diagnosis of lesions of the oral mucosa, and if this is the case: for which clinical questions they are suitable. A strong emphasis is put on in vivo human studies of the oral mucosa.

Endoscopic video autofluorescence imaging may improve the detection of early neoplasia in patients with Barrett's esophagus

BACKGROUND

The aim of this study was to investigate the feasibility of detecting high-grade dysplasia (HGD) and early cancer (EC) in Barrett's esophagus (BE) with a prototype video autofluorescence endoscope.

METHODS

Sixty patients with BE were evaluated with a prototype, high-resolution videoendoscope that has separate charge-coupled devices for white light endoscopy (WLE) and autofluorescence imaging (AFI). Nondysplastic BE appears green on AFI, whereas potentially neoplastic areas appear blue/violet. The BE was first screened with WLE for visible abnormalities and then was examined by AFI to detect additional lesions. Lesions that raised a suspicion of neoplasia and control areas that were normal on AFI were sampled for histopathologic assessment. Finally, random 4-quadrant biopsy specimens were obtained at 2-cm intervals.

RESULTS

A diagnosis of HGD/EC was made in 22 patients; one patient had no visible abnormality, and 21 had endoscopically detectable areas with HGD/EC. In 6 of the latter 21 patients, the HGD/EC was detected with AFI alone; in another patient, HGD/EC was detected with AFI and random biopsies. In 14 patients, HGD/EC was detected with both WLE and AFI; in 3 of these 14 patients, additional lesions containing HGD/EC were detected by AFI alone.

CONCLUSIONS

The results of this study suggest that video AFI may improve the detection of HGD/EC in patients with BE.

Optical biopsy: a new frontier in endoscopic detection and diagnosis

Endoscopic diagnosis currently relies on the ability of the operator to visualize abnormal patterns in the image created by light reflected from the mucosal surface of the gastrointestinal tract. Advances in fiber optics, light sources, detectors, and molecular biology have led to the development of several novel methods for tissue evaluation in situ. The term "optical biopsy" refers to methods that use the properties of light to enable the operator to make an instant diagnosis at endoscopy, previously possible only by using histological or cytological analysis. Promising imaging techniques include fluorescence endoscopy, optical coherence tomography, confocal microendoscopy, and molecular imaging. Point detection schemes under development include light scattering and Raman spectroscopy. Such advanced diagnostic methods go beyond standard endoscopic techniques by offering improved image resolution, contrast, and tissue penetration and providing biochemical and molecular information about mucosal disease. This review describes the basic biophysics of light-tissue interactions, assesses the strengths and weaknesses of each method, and examines clinical and preclinical evidence for each approach.

Distance and angular dependence of intensity ratios in laser-induced autofluorescence techniques

Laser-induced autofluorescence techniques have the potential to be used for the detection of preinvasive human cancer cells. For colorectal and gastrointestinal cancer cells, the light is introduced in vivo through endoscopic means and the probe tip is brought gently into contact with the tissue under investigation. However, it is often assumed that there is no distance or angular dependence in the intensity of the light collected from the probes. We performed an in vitro experiment in which we showed that there was indeed no angular dependence provided the angle of inclination of the probe to normal incidence is small. However, we find substantial fluctuation in the intensities of peaks for changing distances. These fluctuations can be eliminated by considering the ratio of the intensities from two spectral lines.

Time-domain laser-induced fluorescence spectroscopy apparatus for clinical diagnostics

We report the design and development of a compact optical fiber-based apparatus for in situ time-resolved laser-induced fluorescence spectroscopy (tr-LIFS) of biological systems. The apparatus is modular, optically robust, and compatible with the clinical environment. It incorporates a dual output imaging spectrograph, a gated multichannel plate photomultiplier (MCP-PMT), an intensified charge-coupled-device (ICCD) camera, and a fast digitizer. It can accommodate various types of light sources and optical fiber probes for selective excitation and remote light delivery/collection as required by different applications. The apparatus allows direct recording of the entire fluorescence decay with high sensitivity (nM range fluorescein dye concentration with signal-to-noise ratio of 46) and with four decades dynamic range. It is capable of resolving a broad range of fluorescence lifetimes from hundreds of picoseconds (as low as 300 ps) using the MCP-PMT coupled to the digitizer to milliseconds using the ICCD. The data acquisition and analysis process is fully automated, enabling fast recording of fluorescence intensity decay across the entire emission spectrum (0.8 s per wavelength or ~40 s for a 200 nm wavelength range at 5 nm increments). The spectral and temporal responses of the apparatus were calibrated and its performance was validated using fluorescence lifetime standard dyes (Rhodamin B, 9-cyanoanthracene, and rose Bengal) and tissue endogenous fluorophores (elastin, collagen, nicotinamide adenine dinucleotide, and flavin adenine dinucleotide). Fluorescence decay lifetimes and emission spectra of all tested compounds measured with the current tr-LIFS apparatus were found in good agreement with the values reported in the literature. The design and performance of tr-LIFS apparatus have enabled in vivo studies of atherosclerotic plaques and brain tumors.

Novel methods of enhanced endoscopic imaging

Endoscopy has become an essential part of the practice of gastroenterology. Techniques exploiting previously unused properties of light have demonstrated the potential to enhance the ability to make clinical diagnoses without removing tissue as has been standard practice for decades. The term used for many of these techniques is "optical biopsy" and, although not yet widely available, enthusiasm for such techniques has grown as has research in their potential clinical utility.

Temporally and spectrally resolved fluorescence spectroscopy for the detection of high grade dysplasia in Barrett's esophagus

BACKGROUND AND OBJECTIVES

Temporal and spectral fluorescence spectroscopy can identify adenomatous colonic polyps accurately. In this study, these techniques were examined as a potential means of improving the surveillance of high grade dysplasia (HGD) in Barrett's esophagus (BE).

STUDY DESIGN/MATERIALS AND METHODS

Using excitation wavelengths of 337 and 400 nm, 148 fluorescence spectra, and 108 transient decay profiles (at 550 +/- 20 nm) were obtained endoscopically in 37 patients. Corresponding biopsies were collected and classified as carcinoma, HGD, or low risk tissue (LRT) [non-dysplastic BE, indefinite for dysplasia (IFD), and low grade dysplasia (LGD)]. Diagnostic algorithms were developed retrospectively using linear discriminant analysis (LDA) to separate LRT from HGD.

RESULTS

LDA produced diagnostic algorithms based solely on spectral data. Moderate levels of sensitivity (Se) and specificity (Sp) were obtained for both 337 nm (Se = 74%, Sp = 67%) and 400 nm (Se = 74%, Sp = 85%) excitation.

CONCLUSIONS

In the diagnosis of HGD in BE, steady-state fluorescence was more effective than time-resolved data, and excitation at 400 nm excitation was more effective than 337 nm. While fluorescence-targeted biopsy is approaching clinical usefulness, increased sensitivity to dysplastic changes-possibly through modification of system parameters-is needed to improve accuracy levels.

Diagnostic potential of autofluorescence for an assisted intraoperative delineation of glioblastoma resection margins

The intrinsic autofluorescence properties of biological tissues can be affected by the occurrence of histological and biochemical alterations induced by pathological processes. In this study the potential of autofluorescence to distinguish tumor from normal tissues was investigated with the view of a real-time diagnostic application in neurosurgery to delineate glioblastoma resection margins. The autofluorescence properties of nonneoplastic and neoplastic tissues were analyzed on tissue sections and homogenates by means of a microspectrofluorometer, and directly on patients affected by glioblastoma multiforme, during surgery, with a fiber-optic probe. Scan-microspectrofluorometric analysis on tissue sections evidenced a reduction of emission intensity and a broadening of the main emission band, along with a redshift of the peak position, from peritumoral nonneoplastic to neoplastic tissues. Differences in both spectral shape and signal amplitude were found in patients when the glioblastoma lesion autofluorescence was compared with those of cortex and white matter taken as healthy tissues. Both biochemical composition and histological organization contribute to modify the autofluorescence emission of neoplastic, with respect to nonneoplastic, brain tissues. The differences found in the in vivo analysis confirm the prospects for improving the efficacy of tumor resection margin delineation in neurosurgery.

Diagnostic potential of near-infrared Raman spectroscopy in the colon: differentiating adenomatous from hyperplastic polyps

BACKGROUND

Near-infrared Raman spectroscopy is a promising optical technique for GI tissue diagnosis. This study assessed the diagnostic potential of near-infrared Raman spectroscopy in the colon by evaluating its ability to distinguish between adenomatous and hyperplastic polyps.

METHODS

Ex vivo and in vivo Raman spectra of colon polyps were collected by using a custom-built, fiber-optic, near-infrared Raman spectroscopic system. Multivariate statistical techniques, including principal component analysis and linear discriminant analysis, were used to develop diagnostic algorithms for classifying colon polyps based on their spectral characteristics. With the number of samples available, spectral classification of polyps was tested by using a leave-one-out, cross-validation method.

RESULTS

Fifty-four ex vivo Raman spectra were analyzed (20 hyperplastic, 34 adenomatous). The spectral-based diagnostic algorithms identified adenomatous polyps with 91% sensitivity, 95% specificity, and 93% accuracy. In vivo, adenomas (n = 10) were distinguished from hyperplastic polyps (n = 9) with 100% sensitivity, 89% specificity, and 95% accuracy.

CONCLUSIONS

Near-infrared Raman spectroscopy differentiated adenomatous from hyperplastic polyps with high diagnostic accuracy. To our knowledge, this is the first demonstration of the potential of near-infrared Raman spectroscopy for differentiation of colonic polyps during GI endoscopy.

Autofluorescence spectroscopy for in vivo diagnosis of DMBA-induced hamster buccal pouch pre-cancers and cancers

BACKGROUND

Our previous ex vivo study has shown that autofluorescence spectroscopy at 330-nm excitation can discriminate specimens of normal buccal pouch mucosa (normal), epithelial hyperkeratosis (hyperkeratosis), epithelial dysplasia (dysplasia), and squamous cell carcinoma (SCC) taken from DMBA-treated hamsters by using the method of partial least-squares discriminant analysis (PLSDA).

METHODS

This study used a fiber optics-based fluorescence spectroscopy system to measure the autofluorescence spectra of 23 normal, 14 hyperkeratosis, 28 dysplasia, and 10 SCC samples in vivo. PLSDA with cross-validation was used to analyze the autofluorescence spectral data of all samples.

RESULTS

We found that at 330-nm excitation, the autofluorescence spectra of all samples had two main peaks: one at 380 nm and the other at 460 nm. The hyperkeratosis samples had a higher 380-nm emission peak (EP) and a lower 460-nm EP than normal samples. On the contrary, the dysplasia samples had a lower 380-nm EP and a higher 460-nm EP than normal samples. Furthermore, the SCC samples had a much lower 380-nm EP and a much higher 460-nm EP than all other samples. To quantify the spectral changes during the progression of oral carcinogenesis, ratios of the area under the spectrum of 380 +/- 15 nm to that under the spectrum of 460 +/- 15 nm (denoted as A(380 +/- 15 nm)/A(460 +/- 15 nm)) for all samples were calculated. The mean ratio values of A(380 +/- 15 nm)/A(460 +/- 15 nm) decreased gradually from hyperkeratosis to normal, to dysplasia, and to SCC samples. Significant differences in this mean ratio were found between any two groups of normal, hyperkeratosis, dysplasia, and SCC samples. By choosing proper thresholds, PLSDA with cross-validation could provide an accurate identification rate of 86% for hyperkeratosis, of 87% for normal, and of 89% for dysplasia samples. In addition, by choosing a proper threshold, we could separate benign (normal and hyperkeratosis) from dysplasia or SCC tissues with a sensitivity of 92% and a specificity of 95%.

CONCLUSION

Our results indicate that the autofluorescence spectroscopy technique is a useful diagnostic tool for in vivo diagnosis of oral pre-cancers and cancers in DMBA-induced hamster buccal pouch carcinogenesis model.